Power sensors are commonly used to measure the power of radio-frequency (RF) or microwave-frequency (MW) signals. Such measurements can be used, for instance, to characterize the output performance of electrical components used in RF or MW applications such as radar and cellular telephones. A typical power sensor uses a power detector or transducer to convert the RF or MW power to a readily measurable electrical quantity. Power detectors also have applications in many types of RF and MW systems.
A common type of power sensor used for RF and MW measurements is referred to as a diode power sensor or diode detector. Examples of diode power sensors are described in detail in Agilent Application Note 1449-2 entitled “Fundamentals of RF and Microwave Power Measurements”.
Conventional diode power detectors have several shortcomings that tend to limit their performance and flexibility, although, when utilized in a power sensor as part of a power measurement system, sophisticated calibration and data processing techniques can be applied to address some of these shortcomings. One shortcoming is that their bandwidth and sensitivity vary according to different operating conditions such as temperature and input power level. For example, the output voltage of a conventional diode sensor may decrease significantly in response to an increase in the sensor's temperature. Still another shortcoming of conventional diode power sensors is that they exhibit a general tradeoff between detection bandwidth and sensitivity. In other words, bandwidth tends to decrease as sensitivity increases and vice versa. Yet another shortcoming of conventional diode power sensors is that their bandwidth and sensitivity are generally determined by component parameters that are fixed at design time. Accordingly, the sensors are generally designed for a specific targeted application.
In view of these and other shortcomings of conventional power detectors, and power sensors built using them, there is a general need for power detectors and sensors providing stable operation under different operating conditions and capable of adaptive optimization based on the requirements of different applications.